Thermostat



March 15 1927. 1,621,023

G. T. NEWELL,' JR

THERMOSTAT Filed Nov. 12, 1923 M ATTORNEY llamented Mar. 1s, 1927.

UNITED STATES PATENT OFFICE.-

GEORGE T. NEWELL, JR., OF BEVERLY, NEW JERSEY, .ASSIGiNOIxrTOvv WESTINGHOUSE `'EI'.JECTRIG MANUFACTURING COMFAN Y, A CORFORATION OF PENNSYLVANIA.

THERMOSTAT.

Application ined Nvember 12, 1923. serial No. 674,137.

that the temperature ofthe pad may go to 2.2()o F. before the thermostat itself reaches a temperature of 185 F., for which 1t has been carefully adjusted. This is 'caused by A the heat storage characteristic or heat-shielding effect of the metal casing, and is effective upon any change of temperature to' cause the circuit' to be interrupted at either a higher or at a lower temperature than desired.

therethrough, tal'ien on the line II-II ofy Fig. 1,

Fig. 3 is a top plan view thereof with the cover member removed,

Fig. 4 is a view in end elevation thereof,

Fig. 5' is a top plan view of modifica-v tion of the device embodying my'inveiution,

- and Fig. 6 is a view, in side elevation, of the device illustrated in Fig. 5.

A thermostat 11 comprises a casing member l2 that is open at its ends and top, that is of formed land relatively thin sheet metal and that is also of relatively smalldimensions. A return-bent thermostatic strip 13 is located within the casing member 12 and h as one end thereof secured against the inside of the casing 12, a terminal member -let being located between the end of the strip 13 and the casing 12 and strips 1 5 of insulating material being interposed between the terminal member 14 and the'casing and the thermostatic strip respectively.

A plurality of rivet members 1 6 are einployed to secure the hereinbefore described members in proper operative positions relatively to each other, substantially as illustrated in Fig. 2 of the drawing. This construction provides an electrical connection between the casing 12 and t-he one end of the bi-metallic strip 13 through the rivet 16.

rIhe terminal bar lll-is provided with an adjustable screw 17 extending therethrough and through an opening 18 in the casing 12,-whereby it is insulated from the casing moves toward or away from the member 17V in accordance with the temperature to which it is subjected.

A cover member 19, which isrprovided for the open top casing 12, is of relativelv thin sheet metal, and is of substantially channel forni, as illustrated more particul-arly` in Fig. 4 of the drawing. A resis- -vtor member 21 is insulated by a layer 22 of thin electric insulatingV material, such as mica, wound around the same.' .The heating unit, comprising the resistor member 21 and -the insulating material 22 is located inside of the cover member 19,v end portions 23 of which are bent around the unit, as is illustrated more particularly in Fig. t of the drawing, in order. to hold the heating unit in its proper operative position within the cover member.

While I- have illustrated 'a particular method of` securing the heating uni-t against the cover member, I do not wish to be limited thereto, although I have found the hereinbeforeA described method very simple, effective, and one that can be easily employed in the manufacture of the device.

One end of the resistor member 21 is electrically connected to the cover member, an opening 24 being provided therethrough in order` to permit of such connection. An insulated terminal member 25 is provided for the heating unit at the other end of thethe heating unit operatively associated there- Vwith, is placed in its proper operative position on the casing 12, the circuit of a current traversing the thermostat that is connected in series with a heating resistor member (not shown) which it is to control, is as follows:

From the terminal member 14 through the screw 17, bi-metallic strip 13, rivets 16, casing 12, cover member 19, resistor 21 and out through the terminal member 25.

The heat storage capacity of the resistor -member 21 is substantially equal to the heat storage capacity of the assembled device which, as hereinbefore stated is relatively small.

In the construction illustrated in Figs. 1 to 4,inclusive, any heat generated in the resistor 21 is radiated directly through the l outer layer of insulation 22 against the thermostatic strip 13 and the result is that with the proper co-operation of all of the factors entering into thedesign of such a 'thermostatlc structure, the temperature of the bimetallic strip 13 follows very closely to the changes of temperature of the device with which `it is operatively associated, which, as stated above, is usually an electrically heated warming pad.

As the material of such a warming pad is of a relatively low storage capacity and follows the changes of temperature caused by an extended heating element operatively associated therewith very closely, the use of such a device as is embodied in my invention, is very necessary and when such a thermostat structure as herein disclosed is employed, the temperature of the warming pad at which the circuit is interrupted, will l be substantially that for which it has been previously adjusted. That is, the temperature gradient of the thermostat k11 and its heater 21 correspond to the temperature gradient of the heating pad to be controlled, thus permitting the bimetallic strip 13 to respond directly to the temperature of the heating pad.

Figs. 5 and 6 illustrate a modied form of thermostat embodying my invention, the main diference being in the location of the heating unit relatively to the cover member. In this form of construction, the heating unit comprising the resistor 21 and the mica insulation 22 is locatfd on the outside of the :tempes cover member, the integral inturned portion 23 of the cover member 19 being turned outwardly of the cover member instead of inwardly. `f

The action of this form of device is the same as was hereinbefore .described for the form of construction illustrated in Figs. 1 to 4, inclusive.

The device embodying my invention thus provides a relatively small ,and compact thermostat lstructure that may be operatively associated with a device such as an electrically heated warming pad, and will be effective to follow very closely the temperature changes of the pad itself.

The closeness of regulation of the device may be regulated-by proper selections of the length of the resistor wire 21and the resistance thereof. It is possible to so select the resistor member 21 that the temperature of the thermostat structure itself will follow exactly the temperature of the device with which it 'is operatively associated. y

The metal casing may be said to act as a heat shield between the bimetallic strip and a warming pad -or other device, thereby causing the hereinbefore described time lag and the effect of the heating unit on the presen-t invention is to counteract this heat shielding action.

Various modifications and changes may be made without departing from the spirit and scope of the invention, and I desire therefore, that only such limitations shall be placed thereon as are imposed by the prior art or are set forth in the appended claims. p

I claim as my invention:

1. A thermostat structure comprising a bi-metallic strip, a casing therefor, a cover member for said casing extending longitudinally thereof, and coeXtensive therewith, and a heating element operatively mounted on said cover member parallel to said strip and adapted to compensate for the heat-storage capacity of said casing and cover member.

2. A temperature-controlling structure comprising a 'thermostatic electric switch, a metal casing therefor, and means on said casing for causing the temperature of the thermostatic switch to be substantially the same as the temperature outside of the casing during its operative period, said means being parallel to said switch.

3. In a thermostat structure, in combination, a bi-metallic strip, a metal casing therefor, and means comprlsmg a heating lelement mounted on said casing and contion, .a metal casing, a. bimetallic strip said structure when subjected to a varying mounted in said casing, a plurality of tertemperature. mina] members insulatedly supported by In testimony whereof, I have hereunto 10 said casing, and a heating element consubscribed my name this 3rd day of Novem- 6 nected in series circuit relation to Said ter-l ber, 1923.

minal members, casing, and bimetallic strip,

for decreasing the time-temperature lag of i vGrEORGrE'T. NEWELL, JR. 

